Font correction method and device for highway early warning information projection

Abstract

The invention relates to a font correction method and device for expressway early warning information projection, and the font correction method and device can achieve the mobile projection of fonts following an automobile after the rotation angle of the projection device is calculated through the measurement of the speed at a specific road section and then the road slope is calculated. According to the invention, early warning information projection can be carried out on the expressway pavement in an easy-to-identify manner, and efficient transmission of the early warning information is realized.

Description

Technical Field

[0001] The present application relates to the field of image imaging technology, and in particular to a font correction method and device for highway warning information projection. Background Art

[0002] The degree of injury caused by traffic accidents on highways is higher than that on ordinary roads, and it takes longer to restore normal traffic order. Therefore, traffic accidents on highways are more likely to cause long-distance traffic stagnation. For vehicles that are in long-distance traffic stagnation, the probability of a secondary accident is small. Even if a secondary accident occurs, the degree is relatively mild and generally does not aggravate the degree of congestion. For vehicles that are about to join the end of the congested convoy, they need to brake from a high-speed state in a short period of time. When vehicles brake one after another, the reaction time left for the rear vehicles will gradually shorten, greatly increasing the probability of a secondary accident. When the above braking scenarios are superimposed with some dangerous factors, such as fog, rain, entering a tunnel, etc., the probability of an accident is further increased. The superposition of multiple accidents is the basis of the large congestion phenomenon, so early warning of accidents that have already occurred is very necessary.

[0003] Existing technology generally broadcasts the accident information ahead through information panels on highways, but the installation cost of information panels is higher, the conditions for their deployment are harsh, and the number is small, resulting in inflexible information transmission and the warning effect cannot meet expectations. Summary of the invention

[0004] The present invention provides a font correction method for highway warning information projection, which can project warning information onto the highway pavement in an easily identifiable manner, thereby achieving efficient transmission of the warning information.

[0005] The technical solution of this application is as follows: A method for correcting fonts of highway warning information projection comprises the following steps: Step 1: Delimit a warning section on the expressway, wherein the rear of the warning section in the direction of travel is the speed measurement section, and the front is the prompt section; Step 2: Calculate the average speed of the vehicle passing through the speed measurement section, and use the average speed as the passing speed of the vehicle on the prompt section; Step 3: The angle of the projection device when projecting at the starting position of the prompt section is recorded as the initial angle. Based on the passing speed, the initial angle, and the driving time of the vehicle on the prompt section, the rotation angle of the projection device when the vehicle drives to the prompt section is calculated as follows: )= - ; In the formula, Indicates the rotation angle change value, Indicates the passing speed, Indicates the driving time of the vehicle on the indicated road section. Indicates the vertical distance between the projection device and the road surface. represents the initial angle; Step 4: Calculate the slope angle of the prompted road section; Step 5: Calculate the font projection length of the projection device at the starting position of the prompt section when the slope angle is 0°, use this projection length as the first standard length and record the projection distance of the projection device at this time D 起始 ; Use the positioning camera to monitor the vehicle position in real time to determine the display position of the font, calculate the font projection length of the projection device at the display position when the slope angle is 0°, use this projection length as the second standard length and record the projection distance of the projection device at this time D 显示 ; Step 6: Make D 起始 Multiply the ratio of the first standard length to the second standard length to correct in real time D 显示 , the formula is as follows: D 修正= D 2 起始 × D 显示 ; In the formula, D 修正 Indicates the corrected projection distance; Step 7: D 修正 Superimpose the slope angle calculated in step three, and calculate the pitch angle variation range of the projection device relative to the slope of the prompted road section; substitute the pitch angle variation range into the perspective projection model to obtain the font projection screen coordinates, and scale the first standard length based on the font projection screen coordinates to obtain the corrected projection font.

[0006] Furthermore, in step 2, the speed of the vehicle passing through the speed measuring section is achieved by deploying ground sensing coils, as follows: a number of ground sensing coils are deployed in the speed measuring section, and the average speed of the vehicle passing through adjacent ground sensing coils in sequence is calculated based on the induction time and spacing of adjacent ground sensing coils, and the average of the several average speeds calculated is used as the average speed of the vehicle.

[0007] Furthermore, in step 2, an auxiliary camera is installed next to the projection device to monitor the instantaneous speed of the vehicle on the prompt section. When the absolute value of the difference between the instantaneous speed and the speed measurement section exceeds a threshold, the instantaneous speed is used as the passing speed for subsequent calculations.

[0008] Furthermore, in step four, the specific steps for calculating the slope angle of the prompt section are: select several reference points in sequence on one side of the prompt section in the direction of travel, take the projection device as the axis, and select symmetrical points of each reference point about the axis in the prompt section; calculate the height difference between two adjacent reference points on the same side in sequence and use inverse trigonometric functions to obtain the slope angle between the road surfaces of the two reference points, perform weighted averaging on the several slope angles calculated on the same side to obtain two unilateral slope angles, and take the average of the two unilateral slope angles to obtain the slope angle representing the prompt section.

[0009] Furthermore, in step 5, when calculating the projection length of the font, the back end of the font is aligned with the starting position or the display position.

[0010] Furthermore, step seven specifically includes the following sub-steps: Step 1: Convert the pixel coordinates of the projection chip into spatial length coordinates based on the projection device coordinate system through the internal parameters of the projection device, which can be specifically expressed by the following formula: = ; In the formula, , , is the projection device coordinate system, Indicates pixel density, and Respectively represent the origin of the projection chip pixel coordinate system and the projection device coordinate system x axis, y The pixel offset of the axis, Indicates the focal length of the projection device; Step 2: Calculate the coordinates of the projection chip relative to the display position, using the following formula: = ; In the formula, , , Indicates the coordinates of the projection chip relative to the display position, A third-order matrix representing the angle between the projection device and the slope surface; for: ; In the formula, Angle is the pitch angle variation range.

[0011] Step three: solve the font projection screen coordinates when the projection device projects at a pitch angle, and scale the font projection screen coordinates to obtain the corrected projection font. The specific formula is as follows: = = H ; In the formula, It represents the projection distance from the projection optical center to the imaging plane, H Represents the dynamic homography matrix of the projected image-imaging screen, ， ， is the world coordinate system, It is the coordinate point of the pixel of the projection device chip.

[0012] The present application also provides a font correction device for highway warning information projection, including an input device, a projection module, an MCU control core and a posture adjustment stepper motor; the input device uploads the collected vehicle information to the cloud; the MCU is used to transmit a prompt image to the projection module, control the rotation of the posture adjustment stepper motor and parse the cloud data; the projection module is connected to the posture adjustment stepper motor and projects the prompt image to the prompt section.

[0013] Due to the adoption of the above technical solution, the beneficial effects of this application are as follows: 1. In this application, the projection device in step 2 is determined only based on the angle change value and does not contain time information. The rotation speed of the projection device can be adapted to the device of the speed measuring section where the vehicle passes, that is, when the vehicle speed is fast, the projection speed is also increased accordingly, and when the vehicle speed is slow, the projection speed is also slowed down accordingly.

[0014] 2. This application fully considers the impact of road slope and vehicle speed on the projection effect. This application can realize the real-time advancement of projection information on a sloped road, and the font length will be adjusted according to the slope change to ensure the recognizability during the prompt period.

[0015] 3. This application displays prompt information in a dynamic form and realizes ground display. Compared with the traditional static display method at a high place, the prompt method of this application is safer. The driver does not need to look up and stare at the high screen for a long time. He can read the prompt information while observing the road conditions ahead. Moreover, dynamic information is easier for drivers to obtain than static information, and has a higher transmission efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 A schematic diagram of correcting the projection distance in this application; Figure 2 A schematic diagram of an uphill road projection performed by a projection device in this application; Figure 3 A schematic diagram of a downhill road projection performed by a projection device in this application; Figure 4 Schematic diagram for calculating the slope inclination for this application; Figure 5 A system schematic diagram of a font correction device for highway warning information projection provided in this application. DETAILED DESCRIPTION

[0017] Based on the background technology, the present application provides a font correction method for highway warning information projection, comprising the following steps: Step 1: A warning section is defined on the expressway, wherein the rear of the warning section in the direction of travel is the speed measurement section, and the front section is the warning section.

[0018] When a vehicle enters the warning section, it first passes through the speed measuring section to measure the driving speed, and then the projection device performs dynamic projection on the warning section based on the collected driving speed.

[0019] Step 2: Calculate the average speed of the vehicle passing through the speed measurement section, and use the average speed as the passing speed of the vehicle on the prompt section.

[0020] In a specific embodiment, the speed of the vehicle passing through the speed measuring section is achieved by deploying ground sensing coils, as follows: a plurality of ground sensing coils are deployed in the speed measuring section, and the average speed of the vehicle passing through adjacent ground sensing coils in sequence is calculated based on the induction time and spacing between adjacent ground sensing coils, and the average of the calculated plurality of average speeds is used as the average speed of the vehicle.

[0021] Taking into account the projection distance of the projection equipment, the length of the prompt section will not be too long. Under normal driving conditions, the speed of vehicles on the highway will not change too much over a certain distance. Therefore, calculating the average speed of the vehicle on the speed measurement section can simplify the calculation and improve the projection efficiency.

[0022] If the vehicle accelerates or decelerates in the warning section, and the speed change exceeds the average speed range, the real-time speed needs to be used instead of the previously calculated average speed. The real-time speed can be achieved by setting up monitoring cameras, which are also used to monitor the driving time of the vehicle in the warning section.

[0023] In a specific embodiment, an auxiliary camera is provided next to the projection device to monitor the instantaneous speed of the vehicle on the prompt section. When the absolute value of the difference between the instantaneous speed and the speed measurement section exceeds a threshold, the instantaneous speed is used as the passing speed for subsequent calculations.

[0024] Step 3: The angle of the projection device when projecting at the starting position of the prompt section is recorded as the initial angle. Based on the passing speed, the initial angle, and the driving time of the vehicle on the prompt section, the rotation angle of the projection device when the vehicle drives to the prompt section is calculated as follows: )= - ; In the formula, Indicates the rotation angle change value, Indicates the passing speed, Indicates the driving time of the vehicle on the indicated road section. Indicates the vertical distance between the projection device and the road surface. Indicates the initial angle.

[0025] The projection device generally does not rotate by itself. In specific implementation, the projection device can be fixed on a pan-tilt head, and the pan-tilt head program can perform the task of rotating the angle.

[0026] Step 4: Calculate the slope angle of the prompted road section.

[0027] The slope angle of the road section is the angle between the driving road surface at the starting position and the horizontal plane.

[0028] In a specific embodiment, as shown in the attached Figure 4 As shown, the specific steps for calculating the slope angle of the prompt section are: select several reference points in sequence on one side of the prompt section in the direction of travel, take the projection device as the axis, and select the symmetrical points of each reference point about the axis on the prompt section; calculate the height difference between two adjacent reference points on the same side in sequence and use inverse trigonometric functions to obtain the slope angle between the two reference points, perform weighted averaging on the several slope angles calculated on the same side to obtain two unilateral slope angles, and take the average of the two unilateral slope angles to obtain the slope angle that characterizes the prompt section. Figure 4 In the above example, the heights of the four points ABCD are obtained using a surveying instrument. , the vertical distance from the projection device , and the height of the symmetrical points and the vertical distance from the projection device placement The difference in vertical distances between adjacent positions on the same side is , the height difference between adjacent positions on the same side is , for example, take point D and point C, then = , The slope corresponding to the CD section can be obtained as Similarly, the slopes of sections BC and AB can be obtained. , then the slope of section AD = , similarly, the slope of section A'D' can be obtained = . Since the highway can be regarded as a smooth section of road surface within a distance range of 30 - 40m, the road slope angle = .

[0029] Step Five: Calculate the font projection length at the starting position of the prompt section when the slope angle of the projection device is 0°, take this projection length as the first standard length and record the projection distance of the projection device at this time D 起始 ; Use the positioning camera to monitor the vehicle position in real time to determine the display position of the font, calculate the font projection length of the projection device at the display position when the slope angle is 0°, take this projection length as the second standard length and record the projection distance of the projection device at this time D 显示 .

[0030] Step Six: Multiply D 起始 by the ratio of the first standard length and the second standard length to correct D 显示 in real time. The formula is as follows: D 修正= D 2 起始 × D 显示 ; In the formula, D 修正 represents the corrected projection distance; As shown in the appendix Figure 1 , taking the "day" - shaped projection as an example, the starting position of the prompt section is set as the first standard length, and the font projection under the first standard length can be accurately recognized at the driving position. If the font projection is not corrected, as the projection distance increases, the font projection will be stretched on the road surface. Therefore, it is necessary to reduce the projection length of the projection device. It should be noted that D 起始 , D 显示 , D 修正 all refer to the projection distance inside the projection device, not the distance projected on the road surface. D 起始 It can be corrected during the installation of the projection device, that is D起始 can be a fixed position. D 显示 It is necessary to make real-time corrections based on the vehicles monitored by the auxiliary camera.

[0031] In a specific embodiment, when calculating the projection length of a font, the back end of the font is aligned with the start position or the display position.

[0032] Step 7: As attached Figure 2 and attached Figure 3 As shown, D 修正 Superimpose the slope angle calculated in step three, and calculate the pitch angle variation range of the projection device relative to the slope of the prompted road section; substitute the pitch angle variation range into the perspective projection model to obtain the font projection screen coordinates, and scale the first standard length based on the font projection screen coordinates to obtain the corrected projection font.

[0033] In the attached Figure 2 and attached Figure 3 middle, and They are the pitch angle change ranges for uphill and downhill respectively.

[0034] Step 7 specifically includes the following sub-steps: Step 1: Convert the pixel coordinates of the projection chip into spatial length coordinates based on the projection device coordinate system through the internal parameters of the projection device, which can be specifically expressed by the following formula: = ; In the formula, , , is the projection device coordinate system, Indicates pixel density, and Respectively represent the origin of the projection chip pixel coordinate system and the projection device coordinate system x axis, y The pixel offset of the axis, Indicates the focal length of the projection device; Step 2: Calculate the coordinates of the projection chip relative to the display position, using the following formula: = ; In the formula, , , Indicates the coordinates of the projection chip relative to the display position, A third-order matrix representing the angle between the projection device and the slope surface; for: ; In the formula, Pitch angle variation range.

[0035] Step three: solve the font projection screen coordinates when the projection device projects at a pitch angle, and scale the font projection screen coordinates to obtain the corrected projection font. The specific formula is as follows: = = H ; In the formula, It represents the projection distance from the projection optical center to the imaging plane, H Represents the dynamic homography matrix of the projected image-imaging screen, ， ， is the world coordinate system, It is the coordinate point of the pixel of the projection device chip.

[0036] A font correction device for highway warning information projection comprises an input device, a projection module, an MCU control core and a posture adjustment stepper motor; the input device uploads the collected vehicle information to the cloud; the MCU control core is used to transmit a prompt image to the projection module, control the rotation of the posture adjustment stepper motor and parse the cloud data; the projection module is connected to the posture adjustment stepper motor and projects the prompt image to the prompt section.

[0037] In specific implementation, the system is generally composed of a projection module, an MCU control core, and a posture adjustment stepper motor. The projection module is responsible for projecting the image information transmitted by the MCU.

[0038] In this embodiment, as shown in the attached Figure 5As shown in the figure, the AD7850 decoding chip in the projection module is responsible for decoding the image information transmitted by the MCU and converting the standard HDMI / VGA signal into an RGB analog signal that can be recognized by the lens module. The MCU main control adopts STM32F407ZGT6, which is mainly responsible for the posture detection of the projection device and the control of the corresponding posture adjustment stepper motor. Secondly, it is responsible for the analysis of data transmitted with the cloud, such as road warning information and corresponding vehicle speed status information. The MCU main control interacts with the corresponding information in the cloud through the 4G module. Its peripheral circuit MPU6050 is responsible for the posture perception of the current projection device and provides real-time angle feedback. The STM32F407ZGT6 can directly generate a standard VGA signal for the projection module to analyze, identify and project. According to the perception result, the posture of the device is corrected in real time and transmitted to the projection module. Finally, the position of the projection device is controlled in real time through the motor drive to project it onto the road surface where warning information is required.

[0039] Anything not described in this application can be achieved by adopting or drawing on existing technologies. The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A font correction method for highway warning information projection, characterized in that: The following steps are involved: Step 1: Delimit a warning section on the expressway, wherein the rear of the warning section in the direction of travel is the speed measurement section, and the front is the prompt section; Step 2: Calculate the average speed of the vehicle passing through the speed measurement section, and use the average speed as the passing speed of the vehicle on the prompt section; Step 3: The angle of the projection device when projecting at the starting position of the prompt section is recorded as the initial angle. Based on the passing speed, the initial angle, and the driving time of the vehicle on the prompt section, the rotation angle of the projection device when the vehicle drives to the prompt section is calculated as follows: )= - ； In the formula, Indicates the rotation angle change value, Indicates the passing speed, Indicates the driving time of the vehicle on the indicated road section. Indicates the vertical distance between the projection device and the road surface. represents the initial angle; Step 4: Calculate the slope angle of the prompted road section; Step 5: Calculate the font projection length of the projection device at the starting position of the prompt section when the slope angle is 0°, use this projection length as the first standard length and record the projection distance of the projection device at this time D 起始 ; Use the positioning camera to monitor the vehicle position in real time to determine the display position of the font, calculate the font projection length of the projection device at the display position when the slope angle is 0°, use this projection length as the second standard length and record the projection distance of the projection device at this time D 显示 ; Step 6: Make D 起始 Multiply the ratio of the first standard length to the second standard length to correct in real time D 显示 , the formula is as follows: D 修正= D 2 起始 × D 显示 ； In the formula, D 修正 Indicates the corrected projection distance; Step 7: D 修正 Superimpose the slope angle calculated in step four, and calculate the pitch angle variation range of the projection device relative to the slope of the prompted road section; substitute the pitch angle variation range into the perspective projection model to obtain the font projection screen coordinates, and scale the first standard length based on the font projection screen coordinates to obtain the corrected projection font.

2. The method for correcting the font of highway warning information projection according to claim 1, characterized in that: In step 2, the speed of the vehicle passing through the speed measuring section is realized by deploying ground sensing coils, which is specifically as follows: a number of ground sensing coils are deployed in the speed measuring section, and the average speed of the vehicle passing through adjacent ground sensing coils in sequence is calculated based on the induction time and spacing of adjacent ground sensing coils, and the average of the several average speeds calculated is used as the average speed of the vehicle.

3. The method for correcting the font of highway warning information projection according to claim 2, characterized in that: In step 2, an auxiliary camera is installed next to the projection device to monitor the instantaneous speed of the vehicle on the prompt section. When the absolute value of the difference between the instantaneous speed and the speed measurement section exceeds the threshold, the instantaneous speed is used as the passing speed for subsequent calculations.

4. The method for correcting the font of highway warning information projection according to claim 1, characterized in that: In step four, the specific steps for calculating the slope angle of the prompt section are: select several reference points in turn on one side of the prompt section in the direction of travel, take the projection device as the axis, and select the symmetrical points of each reference point about the axis in the prompt section; calculate the height difference between two adjacent reference points on the same side in turn and use inverse trigonometric functions to obtain the slope angle between the road surfaces of the two reference points, take the weighted average of the several slope angles calculated on the same side to obtain two unilateral slope angles, and take the average of the two unilateral slope angles to obtain the slope angle representing the prompt section.

5. The method for correcting the font of highway warning information projection according to claim 1, characterized in that: In step 5, when calculating the projection length of the font, the back end of the font is aligned with the starting position or the display position.

6. The method for correcting the font of highway warning information projection according to claim 1, characterized in that: Step 7 specifically includes the following sub-steps: Step 1: Convert the pixel coordinates of the projection chip into spatial length coordinates based on the projection device coordinate system through the internal parameters of the projection device, which can be specifically expressed by the following formula: = ； In the formula, , , is the projection device coordinate system, Indicates pixel density, and Respectively represent the origin of the projection chip pixel coordinate system and the projection device coordinate system x axis, y The pixel offset of the axis, Indicates the focal length of the projection device; Step 2: Calculate the coordinates of the projection chip relative to the display position, using the following formula: = ； In the formula, , , Indicates the coordinates of the projection chip relative to the display position, A third-order matrix representing the angle between the projection device and the slope surface; for: ； In the formula, Pitch angle variation range.

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